1. Field of the Invention
The present invention relates to an illumination system and a projection device comprising the illumination system. In particular, the present invention relates to an illumination system for transforming a wavelength of a specific wave band light and a projection device using the illumination system.
2. Descriptions of the Related Art
With the gradual improvement in technologies for manufacturing projection devices over recent years, lightweight and slim projection devices have now become the mainstream product in the market. Demands for better designs in the market require the continuous improvement on the design of the projection devices; and accordingly, projection device manufacturers must make great efforts to develop various projection devices that have a smaller volume, a higher efficiency and a better imaging quality to meet the demands in the market.
Referring to FIG. 1 there is shown an illumination system 11 of a projector 1 in the prior art. Instead of conventionally using a single light source to project a light onto a color wheel coated with a fluorescent material, the illumination system 11 utilizes a blue solid-state light source 111, a red light emitting diode (LED) 112 and a wavelength transforming element 113 comprising a green phosphor material and focuses the reflected/transformed light to an imaging system to form an image. However, in the illumination system 11, the blue light can be coupled with the green light and the red light only after being reflected multiple times. As a result, the light energy of the blue light will be attenuated considerably after the multiple reflections. Furthermore, the light emitted by the LED is a scattered light, so multiple light condensing lenses are required to condense the light to improve the light emitting efficiency. Consequently, the projector 1 needs a large internal space to accommodate the multiple light condensing elements, which contradicts the demands for lightweight and slim projectors in the market.
Accordingly, efforts still have to be made in the art to provide a projection device which has an efficient illumination system but a small volume and is also capable of reducing the light energy waste.